For traffic between connected devices, for example, nodes within a multi-node system or processing cores on a chip or processing cores and memory devices, routers are utilized to manage traffic. For example, routers with multiple virtual channels may use round robin priority arbitration schemes in both local arbitration (LA) and global arbitration (GA) stages.
However, the combination of independent round robin schemes may result in priority miss-alignments between the LA arbiter and the GA arbiter, which can increase the interconnect latency by orders of magnitude beyond average network latency. This potential raises concerns about arbitration fairness and delivery predictability for message traffic.
Worst case miss-alignments that may occur consist primarily of persistent loss of priority either at the LA arbiter or the GA arbiter and is a result of independent round robin policies used at each stage. For example, when a message is able to receive a highest priority at the LA arbiter, the GA arbiter may point to a different port when the message finally arrives and the LA arbiter may have already changed the highest priority to a different message that is not the oldest at the input port. This may happen multiple times for the same message, increasing the worst case latency, even up to starvation.